Add documentation for channel macro

src/util/channel.rs

@@ -1,3 +1,61 @@
+/// Creates an implentation of sender which can be used to share an async channel for multiple message types.
+///
+/// # Examples
+///
+/// ```
+/// struct D;
+/// struct A;
+///
+/// enum Msg {
+///   FirstType(D),
+///   SecondType(A)
+/// }
+///
+/// fn main() {
+///   let (tx, rx) = channel::<Msg>();
+///
+///   let d_sender = DSender::create(tx.clone());
+///   let a_sender = ASender::create(tx.clone());
+///   subscribe(d_sender.clone());
+///   subscribe2(d_sender.clone());
+///   subscribe3(a_sender.clone());
+ //
+///   let mut i = 0;
+ //
+///   for m in rx {
+///     i += 1;
+///     match m {
+///       Msg::FirstType(_) => println!("m: D {}", i),
+///       Msg::SecondType(_) => println!("m: A {}", i)
+///     };
+///   }
+/// }
+///
+/// fn subscribe(sender: DSender) {
+///   thread::spawn(move|| {
+///       sender.send(D).unwrap();
+///   });
+/// }
+/// fn subscribe2(sender: DSender) {
+///   thread::spawn(move|| {
+///       thread::sleep(time::Duration::from_millis(10));
+///       sender.send(D).unwrap();
+///   });
+/// }
+/// fn subscribe3(sender: ASender) {
+///   thread::spawn(move|| {
+///       sender.send(A).unwrap();
+///   });
+/// }
+/// implement_sender!(name => DSender, 
+///                   wrap => D, 
+///                   with => Msg, 
+///                   variant => FirstType)
+/// implement_sender!(name => ASender, 
+///                   wrap => A, 
+///                   with => Msg, 
+///                   variant => SecondType)
+/// ```
 macro_rules! implement_sender {
   (name => $name:ident, 
    wrap => $wrap_type:ident,